ADM8840

The ADM8840 combines a charge pump regulator and a Common Line (COM) driver in a single chip solution for use in TFT LCD's. The device provides an LCD controller and grayscale DAC supply voltage of 5.0V (±2%), 2 gate drive voltages of +15V and -15V and a COM driver voltage. This COM Driver voltage alternates the polarity of the Common line voltage every line (or every frame) on the display in order to prevent screen-burn occuring over time. The ADM8840 is powered by a single 3.0V supply.

The ADM8840 has an internal 100KHz oscillator for driving the charge pumps.

The COM Driver section of the ADM8840 can be used to generate the alternate frame or line inversion of the COM line of the LCD panel. It receives the COM clock from the controller with a frequency up to 10kHz and allows programmable conditioning of its amplitude and centre voltage through the use of on-board DAC's. This allows programmable elimination of display flicker caused by the COM inversion.

The COM_OUT amplitude can be programmed from 4.0V to 7.0V in steps of 28mV. The COM_OUT centre voltage can be programmed to 0.9V to 2.8V in steps of 14mV.The ADM8840 provides power up sequencing of the -15V and +15V gate drive outputs, ensuring the -15V starts to power up before the +15V.

The ADM8840 has a number of power save features, including low power Shutdown. The 5.0V output consumes the most power, so Power Efficiency is also maximised on this output with an oscillator enabling scheme (Green IdleTM).

The ADM8840 is fabricated using CMOS technology for minimal power consumption. The part is packaged in a 32- pin LFCSP package.